The purpose of this study was to explore the relationship between cognitive security and extremist behavior in a sample of high school students in Cairo, Egypt. The sample included 245 adolescents aged 16-17 years old. The researcher used two self-report measures, the Cognitive Security Scale and the Extremist Behavior Scale, to assess the participants. The results showed a negative correlation between cognitive security and extremist behavior, indicating that higher levels of cognitive security were associated with lower levels of extremist behavior. Additionally, the study found that cognitive security could be used to predict extremist behavior in this population, as indicated by the statistical analysis. Extremist behavior = 22.134 - 1.444 cognitive security